1. Field of the Invention
The present invention relates to failure detection device for a vehicle that detects a failure in a motor system.
2. Description of Related Art
In recent years, electric vehicles and hybrid vehicles which use a motor as a driving source have been put into practice. Japanese Patent Application Publication No. 11-280513 (JP 11-280513 A) discloses a failure detection device for a hybrid vehicle that includes an engine, a power-generating motor and a driving motor. The failure detection device decreases the reference value that is used to determine whether to discharge the battery that supplies electric power to a motor system so that the vehicle can continue running on the motor when a failure in the engine is detected.
In such an electric vehicle or hybrid vehicle, the drive current, rotational angle or temperature of the motor is monitored and a failure in the motor system is detected based on a detected value. When the failure determination criteria are made strict to increase the failure detection sensitivity, a fail-safe function is frequently executed because a temporal deviation of the detected value that is negligible in a normal situation is immediately determined as a failure. On the other hand, when the failure determination criteria are relaxed to decrease the failure detection sensitivity, occurrence of a failure which requires execution of a fail-safe function tends to be neglected.